--- a/mercurial/branchmap.py	Mon Apr 22 17:46:57 2019 +0100
+++ b/mercurial/branchmap.py	Tue Apr 23 15:49:17 2019 -0400
@@ -341,7 +341,7 @@
                 cachekey.append(hex(self.filteredhash))
             f.write(" ".join(cachekey) + '\n')
             nodecount = 0
-            for label, nodes in sorted(self.iteritems()):
+            for label, nodes in sorted(self._entries.iteritems()):
                 label = encoding.fromlocal(label)
                 for node in nodes:
                     nodecount += 1